The regulations and laws of the United States and many other countries have recently required further reduction of contaminants in waste water, particularly, metallic contaminants. The permitted levels of these contaminants can only be expected to be decreased even more in the future. Because of these environmental concerns, numerous chemical, biological, physical and electrical methods for removing contaminants, particularly metallic contaminants, have been proposed and developed. Some of these methods have utilized humic acids and similar natural organic materials. For example, in U.S. Pat. Nos. 5,906,960 and 6,143,692 to Sanjay et al. the use of solid humic material as an absorbent to bind metals or liquid humic materials to leach and recover metals in a chelated form from contaminated solids is described. The humic materials are selected from the group consisting of soluble humates, insoluble humates, insolubilized humic acid and mixtures thereof. In the '692 patent contaminated ground water is treated by using a cross-linked humic acid solid (HUMASORB-CS™) placed into a cartridge or a trench. In this case, the solid humate removes both metal ions and organics from the water in one step.
In another patent, namely, U.S. Pat. No. 4,081,403 to Takegami et al. the use of solid humic materials as an absorbent for the treatment of waste water is also described. The removal of copper from a liquid medium using surface modified inorganic and organic solid carriers is described in U.S. Pat. No. 4,752,398 to Holbein et al. The possible organic solid carriers in the '398 patent include solid humic materials.
In another patent, U.S. Pat. No. 6,001,769 to Citterbart et al., a humic acid solution is used to elute or extract contaminants from subsurface solids.
In general, the foregoing patents which may be considered to be representative of a larger number of prior art patents, all are directed to using humic acid or its derivatives to either: 1) bind the contaminant to a solid absorbent to reduce the contaminant remaining in the waste water, or 2) to rapidly extract the contaminant from contaminated solids to reduce the potential for future leaching into waste water. In other words, the processes described in the foregoing patents are successful if the contaminants in the converted forms can be reliably removed from the waste water in a solid form or can be rapidly removed from contaminated solids to mitigate future contamination of water contacting the treated solids. However, it is a general object of the present invention to convert low concentrations of metallic contaminants in water to less toxic forms and to reduce their toxicity to an acceptable level without the need for removing the metal from the water or from contaminated solids. This and other objects are achieved by the invention described below.